A communicating groove is injection-molded in an integrated manner on the inner circumference of a two medical agent mixing type syringe for mixing two medical agents contained on the both sides of a piston by circumventing the piston. A conventional syringe mold for a two medical agent mixing type syringe with such a communicating groove formed on the inner circumference is disclosed in Japanese Patent Laid-open Application No. H8-132444.
The syringe mold disclosed in Japanese Patent Laid-open Application No. H8-132444 comprises a cylindrical male die (core cylinder) for molding the inner circumference of the syringe, a slide core for molding the communicating groove which is mounted to move in and out the circumference of the molding male die (core cylinder), and a rotational axis rod incorporated in the molding male die (core cylinder) and coupled to the slide core via a cam mechanism. The slide core moves in and out the circumference of the molding male die (core cylinder) according to the rotation direction of the rotational axis rod.
In this mold, the coolant circulation passage for cooling the molding male die (core cylinder) is formed to penetrate the rotational axis rod, and extends to a molding female die.
There is a molding failure problem due to insufficient cooling of the molding male die (core cylinder) in the conventional mold because it has the cam mechanism for coupling the cam axis to the slide core and the cam mechanism is an obstacle for cooling. The coolant for cooling the molding male die (core cylinder) can flow only in the center portion of the molding male die which is farthest from the molding space where resin is filled. The outer diameter of the flow passage is limited and a sufficient circulating flow cannot be obtained.